Objective for optical apparatus.



C. H. FLORIAN.

OBJECTIVE FOR OPTICAL APPARATUS.

Arrucmon msn un. z5. ma.

1,145,132, Patented July 6, 1915.

UNITED STATES PATENT OFFICE.

CHARLES HENRI FLORIAN, 0F PARIS, lFRANCE, AS'SIGNOB TO SOCIT ANONYME DES ETABLISSEMENTS LACOUR-BEBTHIOT, OF'PABIS, FRANCE.

OBJECTIVE FOB OPTICAL APPARATUS.

To all whom it may concern:

Be it known that I, CHARLES HENRI FLO- RIAN, of 9 Rue Froissart, in the `city of Paris, Republic of France, have invented Improvements in Objectives for Optical Apparatus, of which the following is a full, clear, and exact description.'

The present invention relates to an objective for optical apparatus intended to form an ima whichiis then taken up and transferred ge one or more collecting lenses.

The o ject of the invention is to obtain, after these transfers a plane image notwithstanding the deformation produced by the collecting lenses.

The invention is characterized broadly by the fact that the objective/is constituted in such a manner as tol give a curved image the convexit of which is directed toward the origin o the light, that is to say in the opposite direction to the curvature which is then produced by the field lenses and the collecting lenses which transfer the image. It follows that the initial deformation produced by the objective and the subsequent' deformations causedby thedield lenses and the various collecting lenses are corrected and' that the final image is plane. The objective by means of which this result can be obtained is characterized broadly by the combination of a front divergent system and a rear convergent system, the focal lengths of which are substantially equal and which are separated by an interval which is itself substantiall equal to the common focal distance. he aperture of the objective is substantially e ual to one twelfth of the focal length o the field and is approximately 50.

The imaginary diaphragm of the a paratus, that 1s to say the common base o the incident light cylinders is located between the front divergent system and the rear convergent system at a distance from the front divergent system equal to ,2O-tbs. of the common focal length. The real diaphragm,

that is to say the common base of the light cones issuing from the divergent system, is also located between the two systems at a distance from the front divergent system equal to ith. the common focal length.

l specification of Letters Patent.

Patented July 6, 1915.

Application filed March 25, 1913. Serial No. 756,739.

With vthis arrangement of the novel objectlve the inclination of the emergent penc1ls is small. It follows that if the axes of these pencils are subsequently to be concentrated by a field lens at the center of a collecting lens intended to transfer the 1mage, the convergence of this field lens will be small and, consequently, will only attenuate to a small extent the convexity toward the origin of the light of the image furnished by the objective. The novel 0bjective is also corrected of chromatism and astigmatism for a luminous pencil inclined to the axis at the origin by an angle equal to gths. of the half field. These general results of the novel objective arise, generally speaking, from the choice of the lenses and of the curvatures, but this choice is facilitated and the results are obtained with greater certainty with the combination o-f the optical elements forming the object of the invention.

For certain special applications in which it is desirable to obtain an instrument of the maximum possible length this objective also presents the advantage of furnishing between the front divergent system and the image, a distance equal to three times the focal distance.

This novel objective is applicable in all cases in which it may be useful to obtain an image presenting a curvature the convexity of which is directed toward the origin of l the light. It is thus applicable to terrestrial telescopes having a wide field.

It is applicable to periscopes in which the field lenses and the collecting lenses produce a curvature of the image which is compensated for by the inverse initial curvature produced by the'objective.

It is applicable to certain measuring instruments in which it may be useful to project an image upon a spherical surface or upon a scale drawn in accordance with the generating lilies of a cylinder of small height.

In the case of the periscope:

(l) The astigmatism 'may be corrected as desired as in the example hereinafter given, or it may be retained in the desired proportion according as the astigmatism introduced by the assembla e of successive collecting` lenses and eld enses is canceled or corrected, or if this asti matism still exists Figure II, the curvature of the image beingv accentuated thereby.

(2) The chroma-tism bein corrected for a point of the axis from which the'red and n images are seen in conicidence after the first field lens, the first collectin lens is placed at this point of the axis. his collecting lens, asv it allows the alinement of the im s relatively to its center to persist, is readi y able, by means of a suitable chromatic correction to furnish subsequently perfectly superposed images. The red and green ima s can also be caused to coincide immediate y after the objective as in the rst example hereinafter given. Generally speaking, the lenses of the objective should satis y the following relationship:

. #afee-'dee in which:

tem.

1=the lengths of lens interposed..

da; db,- 'd)\=variations of a, b l between I' the radiations to be com ensated. w=the distance from -tlie image to the convergent system. i

D=the distance point in the axis from which the red and green images are seen in coincidence.

that:

E being the distance from the convergent system to` the divergent system.

. It will be noted that, having 'dispersion selected the of this field lens, its position is determined;

on the contrary, when its` position is deterf mined, its ldi'spersion is also determined.

image-and corrected, D is in a=the foca-l length ofthe convergent'system. Y p' f b=the focal lengthlof the divergent sysfrom the image tothe In assuming (as is very nearly the case) i could' also .be expressed a field lens coinciding with the image and not corrected, or else separated from the articular the distance from the point at -w ich the axes of the luminous pencils Which'emerge from the rear convergent system unite, and consequently equal in the present example, to at least ive times the common focal distance. Furthermore if the following relation is established:

that is to say mits of giving D any desired value and this y condition is 'satisfied by the example given below and corresponding to Fig. 1.

When, -by reason of its a vantages of `simplicity the arrangement illustratedv in Fig. 2 (the second exam le) is employed, even with an uncorrect field lens separated from the image, the self dispersion of this ieldy lens and its separation are con- -nected -by the following relationship that vshouldbe observed in order tomaintain the alinementl 'of the images relatively to the center ofthe first collecting lens in which: D0 is the ldistance to the ima of the point at which the axes of the penclgl; emerging from the rear convergent'system of theo jective unit (that is to say 5F as stated above). D is the distance. to the image of thefpint of -the axis from which the green and re ima es are seen in coincidence as results from t e first relationship and consequently from the constitution of the olg'ectlve. c is the focal distance of the fi d lens employed for bringing the encils back onto the collectin -lens. is t e dis-l tance at which this fiel lens is located from the image and beyond this image.

It should be noted that this relationship way the method of employing the novel objec tive when it is` to be accompanied byv afieldlens whichl is the case with terrestrial telesco es und Periswpes-A or the sake ofclearness the accompany-- ing drawilrlilg `(which `is given byway of example-o y) represents diagrammatically Je'ctive forming the object of the i`n vention, intended fox-a perisoope.

The front diver nt system is formed of two lenses L an L2 arranged in contact (Fig. l). Behind this system is arranged a vergent system is formed of three lenses Air gap: e =26.1

Convergent .L4Rs 23.2 R4 470 It should here be noted that the'selection of the glasses of the lenses L* and L? with the same indices or with indices very approximately the same but with different dis ersive powers, p ermits, without in any way` a ecting the geometrical results furnished by the objective as regards the curvature of the image, the astigmatism and the focal distance, of varying the curvature (R,=R) of' the surface common to the two lenses L* and Lf and consequently of obtaining simply, without further experiments, the value of da, which, in accordance with the relations established above, would suit particular cases different from that which forms the object of the example given above. These special cases may present themselves either because the glasses of different successive batches are not absolutely identical, vor because in a given application, it may be desirable to modify the length of the lens interposed between the two systems (increase, diminution or elimination of the intermediate prism).

The choice of the lenses, the result of verglent system is formed of three 'lenses L31 41 L5' In this example, the Adimensions are as follows:

e,=3 nd=1.5102 ,m6-1.3 e,=4.5 F1613 'v=37.1

which is to cause da to vary at will, without modifying the other magnitudes, permits of -coping with accidental or designed variations -of db and dl.

Instead of constituting the front divergent system as stated, it is possible, provided the relations indicated above are satisfied, to constitute it by a single lens of small dispersion, the concavity of which is always directed towardthe origin of the light. This arrangement has been represented diagrammatically Fig. 2 which shows a single lens Z of special forni arranged in front of the prism P. y

The data are the same as those of the first example except as regards the divergent system. This is cut in a crown of small dispersion.

n=1'.50l to 1.52 Y v=65 to 58 The curvatures will vary slightly with the batch selected. For example, the following mayobtain:

R=25.2 R,=166.7 e=7.5 11.11.5102 v=6 4.3

In this case, the colored images are merely alined and it is not necessary to take them into account in correcting the first collecting lenses and in determining the first field lens, as stated above.

`The arrangements described above are given by way of example only; the forms of the apparatus, the dimensions and detail arrangements may of course vary in all cases without affecting the principle ofthe invention. i

What I claim and desire to secure by Letters Patent of the United States is 1. A lens adapted to give a curved image the convexit of which is turned toward the source o light, comprising a divergent lens and a convergent lens, each of which is adjusted to counteract spherical and chromatic aberration, the lenses having substantially the same focal length, and bein separated by a distance substantially equa to such focal length.

2. A lens adapted to give a curved image the convexity of which is turned toward the source of light comprising a complex divergent lens composed of two elements one bi-concave and the otherl convex in at least one direction, the material of the bi-concave lens being of lower-refracting power than that of the other lens, a triplex lens formed of two bix-convex elements and an interposed bi-concave* element, the index of refraction lof one of the bi-convex elements being less than that of the other elements, the complex lens and the triplex lens having substantially the same focal length and being separated by a distance substantially equal to such focal len h. v

The foregom specification of my improvements in o jectives for optical appa- .ratus signed by me this 14th day of March,

CHARLES HENRI FLORIAN. Witnesses A LUCIEN MEMMINGER,

REN THIRIOT. 

